This invention relates to a traction device mounted to a vehicle wheel and is selectively convertible to road engaging and non-road engaging positions.
This invention has particular application to dual wheels; as exist on large trucks. However, as will be made clear, different forms of the invention can be applied to different types of vehicle wheels.
The invention is considered most applicable to large trucks driven by truck drivers that crisscross the country continuously throughout the year. Invariably a truck driver driving over mountain roads in the winter or even flat land roads in the Northern states, will on many occasions encounter road conditions where snow and/or ice is coated over the road surface.
The conventional wheel tire provides a road contacting surface area that frictionally grips a dry or even wet road surface providing steering and stopping control as well as propulsion over the road surface, but not when that surface is covered with ice and/or snow. The conventional tire surface has poor frictional gripping capability when riding on snow or ice. Whereas several explanations can be given depending on the condition of the ice/snow, what can and often does happen is that the surface of the snow or ice liquefies and forms a liquid film between the tires and underlying surface, thereby eliminating any opportunity for the tire to grip the surface frictionally.
An answer to this dilemma is to provide the tire with metal studs or chains. The studs are embedded in the tire permanently and the chains are designed to be placed on the tire when needed and removed when not needed. In both cases, the projecting metal bites down through the snow or ice (and liquid film) to generate the desired gripping action. Both have problems. Studded tires tear up a dry road surface, i.e., when not covered with snow or ice and most states have strict rules about using them. Most states ban their use except during the harsh winter months. Tire chains are designed to be put on and taken off. However, mounting the chains onto the vehicle tires is an unpleasant task even in ideal conditions which most often is not the case. Weather conditions are likely uncomfortably cold and blustery. Mounting the chains onto the tires can take upwards to an hour or more, and when parked alongside an ice-covered roadway and probably on a graded road, the driver is exposed to potential life threatening risks as other unchained vehicles attempt to pass.
The present invention alleviates or obviates the problems associated with studded tires and the chaining of tires using a retractable studded tire having metal spike-like studs that project from the periphery of the tire and into the road surface or not. In a preferred embodiment, the studded tire is sandwiched between dual tires. The studded tire is designed to expand in circumference when inflated and to contract in circumference when deflated. This is achieved in part by the opposing walls of the dual tires that restrict lateral or axial expansion of the studded tire, thus forcing expansion circumferentially or radially. The expansion characteristics of the tire are designed to provide a circumferential size difference so that when deflated, the tire periphery (circumference) is retracted radially inwardly of the dual tires and when inflated is extended radially outwardly of the dual tires.
The studded tire of this preferred embodiment is not intended to carry the vehicle weight. Essentially the stud portions only of the tire protrude and are projected into the ice or snow, e.g., to a depth at which the dual tires still engage the road surface and support the load. The studs provide gripping action for propelling (or stopping) the vehicle as the studded tire rotates in unison with the dual tires, e.g., the studded tire is mounted on the same tire lugs and the expansion of the studded tire against the opposing side walls, rubber to rubber, resists rotative slippage of the studded tire relative to the load-bearing dual tires.
The studded tire is provided with valving and an air pressure source. The air pressure source may be operated automatically and remotely with direct connection between the air pressure source and the studded tire, or the air source may be an air-pressurized cannister that can be clamped to the valving for inflating the tire. Deflation is enabled, e.g., by a valve mechanism that simply exhausts the air from the studded tire to the atmosphere.
Ideally the inflation/deflation will be accomplished automatically from the truck cab even without the necessity of stopping the truck. The less sophisticated embodiment will allow the driver to stop the truck and in a matter of a few minutes inflate the several studded tires in a fraction of the time previously allotted for mounting tire chains.
An alterative embodiment that is contemplated will adapt the above expanding feature of an expandable studded tire to a single load-bearing tire. A special single tire is produced which provides conventional (non-studded) tread portions which are separated on the tire""s periphery and a studded tire segment is provided between the separated tread portions. Air pressure is separately provided to the studded tire segment. In a preferred form of this alternative embodiment, the studded tire segment is inflated and deflated to expose and retract the studs. In a further embodiment, it is the conventional tread portions that are deflated and inflated to achieve the same result.
Other attempts have been made to provide a gripping member that can be left on the tires and would project into the road surface only when needed. An example of such an attempt: is disclosed in E. Partin, U.S. Pat. No. 2,765,199. Among other differences, Partin does not teach the basic concept of using a studded tire that is expanded in the confining space between dual tires whereby the stationary tire walls induce circumferential expansion of the studded tire beyond the circumference of the dual tires.
Reference is made to the detailed description and drawings referred to therein for a thorough understanding of the invention.